EARTHQUAKE MICROZONATION STUDY ON BATUBESI DAM OF NUHA, EAST LUWU, SOUTH SULAWESI, INDONESIA

Abstract

A study entitled to Earthquake Microzonation on Batubesi Dam of Nuha, East Luwu, SouthSulawesi, Indonesia has been conducted. The study was conducted to obtain a map of peak groundacceleration (PGA) based on the historical seismicity in Sorowako and surrounding area, as well seismicvulnerability index (Kg) based on the measurement of local microtremor on site. The study was conducted ata location between 2.71428 degree - 2.70585 degree South Latitude and 121.3013 degree - 121.3117 degreesEast Longitude. This research is expected to obtain the spatial distribution of the amplification factor (Ao),resonant frequency (Fo), PGA, and Kg to estimate the earthquake hazards potential on location. Themaximum ground acceleration value or PGA obtained by microtremor wave analysis based on Kanai formula.As for determining the Kg used Nakamura or Horizontal to Vertical Spectral Ratio (HVSR) method. Basedon the results of data processing obtained the value of PGAmin is 0.079 Gal. at the point of MSBB25,PGAmax is 0.381Gal at the point of MASBB21, and PGAavg is 0.18 Gal. As for the Kg obtained value ofKgmin is 0.28 at the point of MSBB22, Kgmax is 43.42 at the point of MSBB10, and Kgavg is 9.81. Whilebased on the interpretation by means of the PGA value has been estimated that the MMI intensity is in therange of VII-IX with seismic risk level at a medium range of III until great of III. By means of the dominantfrequency (fo) and dominant period (To) was estimated that soil classification for Kanai in the range of IIuntil IV and the range of B - C for Omote-Nakajima.